1. Field of the Invention
The present invention relates to a data-storage apparatus and a data-storage method, which manage and store various data items such as AV data, in the form of files, under the control of a host apparatus, and to a recording/reproducing system which has a host apparatus and a data-storage apparatus. More particularly, the invention relates to a data-storage apparatus and a data-storage method, which has a recording medium such as disc on which the data-transfer rate changes in accordance with the data-access position, and a recording/reproducing system.
2. Description of the Related Art
The FAT file system is a file system for use in external storage apparatuses provided in host apparatuses such as personal computers (PCs). Among the external storage apparatuses are hard disc drives (HDDs) and recording media each having a nonvolatile solid-state memory (e.g., Memory Stick (trademark) manufactured by Sony, Smart Media (trademark) manufactured by Toshiba, Compactflash (trademark) manufactured by San Disk, and multimedia cards).
The FAT file system uses two data items. The first data item is a file allocation table (FAT) that shows where on a recording medium individual files are recorded. The second data item is a directory item that shows where in the directory the files and their attributes exist.
Generally, the recording medium has two areas, one dedicated to the FAT and the other dedicated to the route directory. The PC receives the information necessary to access any file, from a recording/reproducing apparatus through a PC interface (e.g., small computer-system interface (SCSI), integrated drive electronics (IDE), IEEE1394, universal serial bus (USB), or the like). The PC then controls the recording/reproducing on the basis of the information it has received.
When a file is written in, for example, an HDD, it is recorded in an empty cluster. Upon completion of the file writing, information representing which cluster will be used next is written in the FAT. To erase the file, the data written is preserved, and the FAT item corresponding to the cluster used is rendered an empty cluster. To read the file, the start cluster address of the file is obtained from the directory item. The FAT item that corresponds to the start cluster address is read. From the FAT item thus read, it is determined which cluster contains the data file to be read. The data file is then read from the recording medium.
To transfer data between the host apparatus and the HDD, a disc cache apparatus may temporarily store the information to be written in the hard disc or the information read from the hard disc. The speed of accessing the hard disc can then be apparently increased. As in the technique described in Patent Document 1 (Jpn. Pat. Appln. Laid-Open Publication No. 11-45210), a nonvolatile semiconductor memory, such as a flashEEPROM (electrically erasable and programmable read only memory), may be used as cache. In this case, the content of the cache does not have to be written back into the hard disc before the power switch is turned off. This would be very convenient.